Method of and apparatus for proportioning and mixing combustible fluids



Sept. 28, 1937. E. x. sHMlDT 2,094,192

METHOD OF AND APPARATUS FOR PROPORTIONING AND MIXING COMBUSTIBLE FLUIDS Filed April 8, 1935 1 2. bn '8 /9 59 L L l tTo 4Z 41 4o 45 sa 57 #56 f l 54 5, '9. l 4 f fzo n z4-z5 a 44 :21:: 52 55 342355 l 5l 6 ,4 l4aaL w I 47 l I8 (4a 49 43 53 52 I /0 -g9 7 6 9 l5 [l J 5 lz '7 1 z w32' Q "Y '18,49 59 L L z f` sa 4f 57 :.56 f H -54 I9 60a 6o 5g VV-M n b 0 60 6l21 7/ 6l -f/a 44 l A im 4 w '62 os 6l 68 I l '59 65 66 67 5 5a I l? @JI T- @www 2 'sheets-sheet 1 v Sept. 28, 1937. E, X SCHMlDT 2,094,192

METHOD OF AND APPARATUS FOR PROPORTIONING .AND MXING COMBUSTIBLE FLUIDS v Filed April 8, 1935 2 Sheets-Sheet 2 LIL?" @MQ i 1B/f. t; 59 9&3, .Ll/zl I@ 74 38 /75 n:` 45 F z V57 56- M L I9 l 37 55 az 5436 a 30 5 l 78 78 4| 47 [8 I4 4,9 #82' 7 6 lo Z9 7', el

. 1 A 5 n- '2' 80 M Patented Sept. 28, 1937 UNITED sTA'rlzsl PALTFN'F oFF-ICE METHOD OF AND APPARATUS FOR PRO- PORTIONINGAAND MIXING COMBUSTIBLE FLUIDS Edwin X. Schmidt, Whitefish Bay, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation oil Delaware Application April 8, 1935, Serial No. 15,267 16 Claims. (Cl. 48-180) methods of proportioning and mixing flows of combustible gases whereby a flowing combustible gaseous mixture of predetermined heating value p er `finit volume is insured. I

Another object is to provide novel methods of accomplishing the aforementioned desirable result under conditions of variation in certain characteristics of one of the constituent combustible fluid flows.

Another and more specific object is to provide novel methods of gas mixing control of ,the socalled butane-air plant type. Another object is to provide methods of the aforementioned character wherein the proportioning is effected in accordance with and to compensate for variations in the 4specific gravityyof one of the constituent iluids.

Another and more specific object is to provide methods of the aforementioned character whereinvariations in the value of the specific gravity of one of the constituent iluids are measured and utilized to effect maintenance of a substantially constant heating value per unit volume of the final composite flow.

Another object is to provide simple and efcient apparatus for carrying out the methods aforementioned.`

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate certain embodiments of the invention which will -now be described, -it being understood that the invention is susceptible of embodiment in other forms with- .in the scope ofthe appended claims.

In the drawings, Figure 1 illustrates schematically and diagrammatically a gas Vmixing control system constructed in accordance .with my invention.

Fig. 2 illustrates,schematically and diagrammatically a slightly modied form of the gas mixing control system shownin Fig. l, and

Fig. 3 illustrates schematically and diagrammatically another modified form of the gas'mixing control system shown in Fig. 1,-the system of Fig. 3 providing for utilization of a pair of specific gravity meters, with the novel results hereinafter described.

- It is well known that a definite relationship,

exists between the respective heating values per unit volume of the paraine series gases (such as tice.

of said gases. This yrelationslriip may be expressed by the equation: H=1532.7G+142.1;

,Where H is the heating value per unit volume of the gas at standard conditions of 32 inches of f mercury (barometric pressure) and 4at a'temper-` atureY of 60 degrees F., and G is the specific gravity of the gas.

By volumetrically proportioning the vapor from butane liquid orpropane liquid, or a mixture o f such vapors, with air, a combustible gaseous mixture suitable for distribution in small communities may be provided. This combustible gasecus mixture should preferably have a constant heating value per unit volume. 'Ihis can be accomplished by employment of a calorimetric device adapted to continuously' ascertain the heat ing value per unit volume of the iinal mixture-'- said calorimetric device being adapted to automatically eiect proper proportioning of the constituent .combustible fluid ows whereby said heating value perlA unit volume is maintained substantially constant. Systems of `the character just mentioned are disclosed in my prior Patent No. 1,912,044, dated'May 30, 1933, and in my prior Patent No. 1,933,641, dated November?, 1933.

With my present invention, however, it is proposed to eiect maintenance of a substantially constant heating value per unit volume of the lnal mixture in accordance with the determinations of a specic gravity ymeter which responds to variations in the specic gravity of the vapor per se (whether butane or propane vapor, or a mixture of such vapors) By providingfor employment of a specie gravity meter or meters, insteadoi a calorimeter of the required degree of accuracy in operation, a substantial saving in the initial cost of the installation and in the maintenance expense may be eiected.

It has heretofore been proposed to employ speciflc gravity meters on the final mixture for ccntrolling the proportioning of the `constituent fluids. This procedure, however, is incorrect and relationship exists between the heating value per unit volume of the final mixture and the specic gravity thereof when the specific gravity of the hydrocarbon vapor remains c0nstant,this latter condition is substantially unattainable in prac- As an example, a 550 B. t. u. mixture of propane vapor and air will have a specific gravity of approximately 1.0835, whereas a 550 B. t. u.: vmixture of butane vapor andair will have a specic gravity of 1.172. Inasmuch as a mixture or butane vaporand air having a specic gravity of Y 1.0835 has a heating value of only 267 B. t. u. per cubic foot,\it is manifestthat the method of control of proportioning as just described is subject to serious errors-it being understood that in any given installation lthe specific gravity of the hydrocarbon vapor is subject to uncontrollable variations.

I have found that by employing a suitable form of diierential-pressure type ilow ratio control, or by employing mechanically coupled positive pressure blowers, itis possible to volumetrically'proportion flows of hydrocarbon vapor -and air with a fair degree of accuracy. Then by employing a specific gravity meter to continuously ascertain the speciic gravity of the hydrocarbon vapor and by utilizing the operation of the specific gravity meter to effect a change in the volumetric proportioning provided by the differential-pres,-

sure type flow ratio control or by the mechanical-g j ly coupled positive pressure blowers in the desired relationship to said specific gravity de-` termination, the desired constant heating value -per unit volume of the nal mixture will bev maintained.v Referring first to Fig. 1 of the accompanyin drawings, the numeral 5 designates a conduit through which a continuous and predetermined constant volume of air or other dilutingI gas whose specific gravity and heating value per unit volume are lower than the specic gravity andv heating value per unitA volume of propane vapor is adapted to be supplied through the medium of a. blower or pump 6,--which is preferably driven by an electricmotor (not shown). The inlet 1 of pump 6 may be open to atmosphere, or the v same may be connected with any other suitable source of supply of a fluid having the charac-` teristics just mentioned. Conduit 5 is provided atv an intermediate point in its lengthwith' a' xed orice 8 which functions in a well known manner tov produce a pressure difference or pressure drop. The value of said pressure diierence `is vascertained through the medium of a dia' phragm 9 which is enclosed within a housing I0.

A small A*pipe I I -provides for transmission of the iluid pressure at the upstream side of orifice 8-to the lower surface of diaphragm 9, and a small pipe I2 provides for transmission of the fluid pressure at the downstream side of orice 8 to the upper surface of diaphragm 9. Diaphragm 9. has attached thereto a. rod 'I3 which is slidable with a fluid-tight t through-an opening provided in thev lower wall of a chamber |4,-the upper end of rod I3 being adapted to The tank or container I8 may be of a suitable or desired'size Ito satisfy the requirements of the particular installation, 4and it may be assumed that-the same is partially filled with a volatile liquid hydrocarbon such as `butane,-the space not occupied by the liquid being utilized to provide for temporary storage of the generated vapor. A conduit I9 .leads from the upper endA of said tank, and said .conduit is provided with a well known form of valve 20 which is operable automatically to lmaintain a substantially conj pipes.

,posite ends of a cylinder 32 whose piston 33 is with a fixed orifice 2|, and the value of the presv sure drop across said orifice is determined through the medium of a diaphragm 22 located within a housing -23, and the Smau pipes 24 and 25 which respectively afford communication between the upstream side of orice 2| and the upper surface of said diaphragm and between the downstream side of oriiice 2| and the lower surface of said diaphragm.

Attached to and extending downwardly from diaphragm 22 is a rod 26, the lower end of which is slidable with a fluid-tight iit through an opening provided in the upper wall of chamber' I4,- said lower end of rod 26 being adapted to engage a nozzle 21 which i's pivoted at its right hand end within said chamber. Interposed between and slidable with respect to the nozzle 21 and rod I5 is a disk or block 28, the position of which maybe initially adjusted to provide the ydesired proportionality between the volumetric rates of flow of air through conduit 5 and vapor a through conduit I9, and the position of which disk 28 is Iadjusted automatically as hereinafter described to compensate for variations in the specific gravity of the vapor flowing through conduit I9. y

As shown the nozzle 21 is connected by pipe 29 with conduit 5, whereby a continuous jet of air under pressure is emitted therefrom. The air in chamber I4 is preferably vented, as by means of the relatively small pipe or opening I4. It is to be understood that any other suitablesourc'e of fluid under pressure might be employed for said nozzle. A pair of pipes 30 and 3| penetrate the left hand end wall of chamber I4 and have their ends arrangedin close adjacency to each other,`-the arrangement being such that when nozzle 21 is in an intermediate or neutral position theiluid under pressureis equally divided between the two pipes 30 and 3|, whereas upon movement of the nozzle in'one direction or theother from said neutral position a major portion or all of the fluid is injected into one of said Pipes 30 and 3| communicate with opstituent iiuid flows the values of the pressure differences across the orices 8 and 2| will bear the desired relationship to each other, and in consequence the nozzle 21 will move to its neutral position to retain the piston 433. and valve 31 in their respectiveadjusted positions. The'system as thus far `described. is in general quite similar Y to the systems disclosed inY my Patents Nos. 1,912,044 and 1,933,641 aforementioned.

However,'in order to provide a substantially constant heating` value per unit volume of the gaseous mixture. flowing in conduit I1 I`provide` supplied by pipe 38to a well known form of 'specificn gravity meter designated in general by the numeral 39. -Said meter is calibrated to provide a range of measurement from 1.5 (which is substantially the specific gravity of propane) to 2.0 (which is substantially the specic gravity of butane). The indicator or pointer 40 of said meter is formed of conducting material for cooperation with a resistance element 4I, the lopposite ends of which are respectively connected by conductors 42 and 43 with the ends of another resistance element 44,-said conductors being respectively connected with the terminals of a battery 45 or other suitable 'sourceof direct current supply.

A contactor 46 is adapted to cooperatively engage resistance element 44,6 said contactor being carried by a traveling nut 41 which is adapted to be driven by the threaded shaft 48a connectedwith motor 48. Nut 41 has attached thereto one endl of a rod `49 the other end of which is attached to the disk or block 28 aforementioned. Motor 48 is of the split-field reversible type, the commonv terminal'50 thereof being connected by conductor 5I with line L2 of a suitable source of currentsupply, and the split-field terminals 52 and 53 are respectively electrically connected with the stationary contacts 54 and 55 of a polarized relay, the movable contactor 56 of which is elec-y trically connected with line L1 of saidl source of current supply. The operating winding 51 has its opposite ends respectively connected with .the contactors 4B and 46', wherefore a Wheatstone bridge circuit is provided.

, Thus it may be assumed that the parts aforedesvcribed are so calibrated that in the adjusted positions thereof-illustrated the volumetric rate of ow of the hydrocarbon vapor through conduit I9 is so proportioned with respect to the volumetric rate of ow of airthrough conduit 5 as to provide a flowing mixture in conduit I1 having a heating value per unit volume of 550 B. t. u., In the event of an increase in the specific gravity of the hydrocarbon vapor flowing through conduit i9 it is necessary to definitely vary the volumetric` rate of flow thereof in order to maintain the aforementioned heating value per unit volume (550 B. t. u.) ofthe mixture ilowing in conduit Il. Accordingly upon movement of contactor il@ toward the right in response to said increase in specific gravity of the vapor, the aforementioned Wheatstone bridge circuit l will be unbalanced to a corresponding degree.

It may be assumed that such unbalancing will` cause engagement of the relay contactor 56 with contact 54 with vresultant energizationof motor 48 to effect movement of contactor 46 toward the right to effect rebalancing of the Wheatstone bridge circuit. Simultaneously with such movement of `contactor 46 the disk 23 is moved toward' 31 will so vary the volumetric proportionality between the constituent fluid flows as to provide or maintain a substantially constant heating value per unit` volume c-f the final mixture owing in vconduit I1. y

Upon a decrease in specic gravity of the vapor flowing in conduit I9 the aforedescribed elements will function in a similar manner, but in an oppolsite sense, to effect the required degree of opening movement of valve 31 whereby the required volumetric proportionality Abetween the flows of hydrocarbon vapor and air is provided to produce a final mixture of the desired' quality or heating value per unit volume. l

As will be understood by those skilled lin the art, even though butane liquid alone or propane liquid alone (of usual commercial quality, or'

character) is employed in container I8, the vapors generated by the respective individual liquids will be subject to inherent variations in specific gravity, as the generation of vapor'proceeds,-due to the fact that the more volatile constituents of the liquid are initially released at a relatively more rapidvrate than the less volatile gases. position of the residual liquid changes so that as the tank gradually empties the vapors approximate or comprise the less volatile of the hydrov volume of the inal mixture of vapor and air under these inherent conditions of variation in specific gravity of the vapor; but the same also inherently compensates for variations in the specie gravity of the vapor dueto alternate use of dierent hydrocarbon liquids of the paraine As evaporation progresses the` comseries, or to variations incident to use of a mixture of two or more dierent liquids of the aforementioned character. I

As willbe understood, the specific gravity meter 39 is calibrated to provide for determination of the range of specific gravities which it is contemplated shall be encountered in the particular installation. In like manner the resistances 4I and 44 are calibrated in /accordance with said range of specific' gravities and so arranged with reference `to each other as to provide for proper control of the polarized relay aforedescribed.

The embodiment of my invention illustrated in Fig. 2 is in many respects like that shown in Fig. 1, and corresponding parts have been given like numerals of reference in the two figures. In Fig. 2 I have substituted for the pump or blo-wer Ii of Fig. 1 a positive pressure blower or pump 58 of va. well known form,-said pump being arranged to be drivenV at a constant speed by an electric motor 59,' which may be supplied with current from lines L1, L3, or from any other suit-` able source. A volumetrically constant flow of air`from conduit 5 to conduit I l, is thus effected Located Within conduit I9 is another positive pressure bloweror pump 6i! which may be similar in construction Abut preferably smallerin size than the blower 58 aforementioned.

Blower 6b, as shown, is provided with a pair of rotary impellers 60, 60h, which are meshed with or geared to each other. Impeller Illb is driven by a shaft bla which is in turn driven by a suitable form of variable speed transmission gearing designated by the numeral 6i. Gearing 6I is connected by shaft Iilb with fmotor 59, whereby blowers 58 and 65 are mechanically connected with each other. The means for Varying the speed of blower @il with respect to the speed of blower 53 comprises a sprocket wheel 62 which is adapted to adjust the variable speed gearing 5l in a sense and to a degree corresponding with the direction and degree of operation ofv a sprocket lwheel 53. Wheels 52 vand 63 are con-` nectedby an endless chain 64.

Wheel 63 is adapted to be driven through the medium of suitable' speed reducing gearing 65 by an electric motor 66 of the split-field reversible type'. The common terminal of the eld windings of motor66 is connected by conductor 61 with .line L. The individual terminals of said eld windings are connectedv by conductors 68 and 69 with the respective stationary contacts 54 and .55 of a polarized relay of the character described in connection-with Fig. 1. The movable contactor 56 of said relay is connected by conductor 10 with-line L1. 'I'he operating winding 51 of the polarized relay is electrically connected with the combined indicating arm 'and contactor 40 associated with ,resistance 4| and with the vcontactor 46 associated with resistance 44.

Contactar 46 is carried by a traveling nut or block 1|, the position of which is controlled vby the direction and amount of rotary movenent of a threaded shaft 12 which is rigidly connected with the aforementioned sprocket wheel 63. Nut 1| is restrained against rotary'movement. as by means of a suitable guide-bar or rod 13 with which saidl nut has sliding engagement. 'I'he aforedescribed elements of the Wheatstone bridge circuit are adapted to function in the manner set forth in connection with the 'system of Fig. 1'. Thus-with the various elements shownv in` Fig. 2 initially adjusted to so volumetrically proportion thev rate of flow of the hydrocarbon vapor (such as butane) through conduit I9 with respectto thel rate of iow of air through conduit 5 as to provide a flnal mixture in conduit |1 of predetermined heating value per unit volume (say, 550 B. t. u.), the Wheatstone bridge cir-- metric proportionality will be maintained automatically by the operationv of blowers 58 and 66 at the relative speeds thereof preselected by the adjustment of the aforementioned gearing 6|.

However, upon an increase in the 'specific gravity of the vapor owing in conduit/'I9 the combined indicator' and contacto if 4|l`y of meter 39.

fromC line l..2 through one of the eld windingsv of motor 66, and through Contact 54, contactor 66, and conductor 16 to line',I.|1,- Motor 66 will thereupon operate in a direction to eiectdownward .movement of the contactor 46 associated with resistance 44, and such y,movement will continue until the bridge circuit is brought into a balanced condition.

. During such movement .of contactor 46 the "'to'radjust the gearing 6| to reduce therelative .rate oi' operation of blower 66,' so-that upon rebalancing of thev bridge circuit the `volumetric rate of supply of hydrocarbon vapor by pump 66 will have been so reduced as to provide (upon mixture thereof with the air supplied by blower 58) the predetermined heating value per unit volume (550 B. t. u.) of the mixture owing in conduit I1.

Upon a decrease in the specific gravity o f the4 hydrocarbon vapor owing in conduit'ls the combined contactor and indicator 46 will Vbe moved toward the left to effect unbalancing of the 75 line I.'2 by conductor61 through` said other field chainndf-sprocket gearing 63, 64 and 62 acts' winding, by conductor 69 to contact 55 and contactor 56, and by conductor 16 to line L1.' Motor v|56 is thus operated in a direction to effect,up'

ward movement of contactor 46 with respect to resistance 44 whereby the bridge circuit is rebalanced,-the aforementioned gearing 63, 64l 62 acting simultaneously to eiect adjustment of gearing 6| whereby the rate of operation of blower 66 is increased to increase' the volumetric rate of supply of the hydrocarbon fluid by blower 60' with reference to the volumetric rate of supply of air by blower 58. The result of the adjustments Aafor'edescribed is that the heating value per unit volume of the final mixture owing through conduit l1 is maintained substantially constant. c

In Fig. 3 I have shown another modification of the gas mixing control system illustrated in Fig. 1. Many of the parts shown in Fig. 1 are utilized in constructing the system shown in Fig. 3, andv such parts have been; given like numerals of reference.' In Fig. 3 I have shown van additional specific gravity meter 14 whicl communicates by piping 15 with conduitll to provide for continuously ascertaining the specific gravity of the mixture of hydrocarbon vapor and air flowing in said conduit.

Meter 14 is calibrated to indicate a range of values between 1.08 at the left (which is approximately the specific gravity of aproper mixture of propane vapor and air, having a total heating value per unit volume'of 550 B. t. u.) and 1.17 at the right (which is approximately the specic gravity of a proper mixture of butane vapor and air, having a total heating value per unit volume of 550 B. t. u.). Meter 14 has associated there with a'resistance element 16* and an indicating arm 11 which acts as a cooperating contactor for said resistance. Resistances 4| and 16, contactors 46 and 11 and the operating winding 51 of the polarized relay are arranged in the form of a Wheatstone bridge circuit, which includes the battery 45.

As in the devices aforedescribedthecontactor 56 of the polarized relay is' adapted upon unbalancing of the bridge circuit to engage contact 54 or contact- 55, to effect operation of a motor 18 in Vone direction or the athensaid motor through itsthreadd shaft 18 being adapted to effect movement of nut 41 in one direction or the other.

tion and degree of movement of the piston within cylinder 32, whereby the elements.34, 35 and 36 'eiect the required direction and degree of adjustment of valve 31. y

In a device ofthe character disclosed in Fig. 3 I prefer to employ an additional small motor 19 which may be connected, by a manually operable switch 86, across lines L1, L2. Motor 19 carries a rotatable cam member 8| which is arranged to e'ect alternate closure and opening of a switch f II, whereby the circuit of motor 18 is alternately completed and interrupted during engagement of the polarized relay contactor 56 with one or the other of th'e contacts 54 or 55. The primary purpose of switch 82 is to insure adjustment of valve 31 intermittently-or in steps, whereby a given adjustment thereofis permitted to take' effect in respect of la variation in the' specific gravity of Aswill be apparent upon careful consideration of meter 39 the same is calibrated to ,indicate at termediate indicating points to measure the value of various mixtures of thesehydrocarbon vapors. In like manner the meter 14 is calibrated to indi- 1 cate at the left hand side the specific gravity (1.08) of a proper` mixture of propane vapor and air and at the right hand side the specific gravity (1.17) of a'proper mixture of butane vapor and airf,-the intermediate values corresponding with the specific gravities of proper mixtures of propane and butane vapors jointly with -air to' provide a composite fluid having the aforementioned heating value per unit volume of 550 B. t. u. The values of resistances 4I and 16 are properly calibrated and related to each other, and the arrangement ofthe Wheatstone bridge parts is such that the contactors 4D and 11 must have like angular positions to effect balancing of the bridge circuit.

More particularly, with the parts in the positions thereof illustrated in Fig. 3, let it be assumed that the specific gravity of the hydrocarbon vapor flowing-in conduit I9 changesto 2.0 (which is the specic gravityof butane vapor) The contactor 49 Will thereupon move to the extremeright hand end of resistance 4|,.with consequent unbalancing of the bridge circuit.

Due to the last mentioned change in the specific gravitygof the vapor flowing through conduit I9, the volumetric rate of flow thereof through orifice 21 will be slightly reduced. Within a very short period of time the specific gravity of the iiowing mixture of gases in conduit I1 will change. time delay beforethe specific gravity meter 14 can act to show the resulting change in the specic gravity of the mixture flowing through conduit I1, the' motor 18 will have begun to adjust the ratio of the ow through conduit I9 (in this instance effecting movement of valve 31 toward closed position). Shortly thereafter the specific gravity meter 14 will act to show lthe actual specific gravity of the mixture flowing through conduit 11,*and from that time on motor 18 will operate the m-edia aforedeScribed to effect adjustment of valve 31 until indirectly; throughthe change in ratio of the pressure drops across orifices 2l and 8, the heating value per unit volumeiiowing in conduit I1 is again of the Vdesired or predetermined value. As aforeindicate'd attainment of the last mentioned result will be indicated by corresponding angular positioning of the'contactors 40 and 11 of specific gravity meters 39 and 14. N

'From the foregoing it will be apparent that the .system disclosed in Fig. 3 not only compensatesfor variations in the specic gravity of the hydrocarbon vapor supplied, but also compensates for any inaccuracies or imperfections in the mechanical means for effecting volumetric proportioning of the hydrocarbon vapor and air. For instance, if the orifice 8 in conduit 5 should become further restricted `due to corrosion, accumulation of dust or other sediment, etc., the resulting decrease in the 'volumetric rate of flow of air would affect the value of the specific gravity of the mixture iioWing in conduit I1, and the resultant movement of contactor 11 would effect a corresponde ing degree of unbalancing of the Wheatstone bridge circuit. As a result the motor 1,8 would be operated in the `manner aforedescribedto effect the requiredV direction anddegree of adjustment of valve 31 to provide forrebalancing the bridge cir- Inasmuch as there is a slight balancing of the bridge circuit would cause in-` termittent operation of motor 18 to gradually effect opening movement of valve 31, and such adjustment would be stopped automatically uponmovement of contactor 11 toward the left to an angular positioncorresponding with thatof contactor 40,-thus indicating and insuring attainment of the proper value of the specic gravity of the mixture flowing in conduit I1. The operating advantages of the system illustrated in Fig. 3 will be apparent to those skilled in the art.

In the several systems herein disclosed it is contemplated that the pressure of the vapor ilowing in conduit I9 shall be definitely proportional to, and preferably equal to, the pressureof air flowing in conduit 5. In practice I prefer that each ow vof fluid shall be at substantially Vatmospheric pressure. It is to be understood that the. specific gravity meters herein' disclosed are of atype adapted to .be subjected to the gravity effect 'of`a continuously owing sample of the test fluid. The sample, when tested, may be burned, or discharged to atmosphere or returned in any suitable manner to the main flow of hydrocarbon vapor.

What I claim as new and desire to secure by YLetters Patent is.:

1. In a gas mixing control system, in combi'- nation, a branch conduit through which a hydrocarbon vapor of the parafne series is adapted to flow, another conduit through which air is adaptedv to ow, a main conduit into which said branch conduits discharge to provide for mixture of said oWs of vapor and air and to provide for conveying the composite fluid so produced to a point or points of use or storage, means for initially proportioning the volumetric rates of flow of vapor and air to provide a cornposite fluid of a preselected heating value per unit volume, means for continuously ascertaining the instantaneous' value of the specific gravity of the hydrocarbon vapor, and means responsive to variations in said instantaneous valuel v per unit volume of said composite fluid.

2. In a gas mixing control system, in combi-- nation, a branch conduit through which a hydrocarbon vapor of the paraffine series is adapted( to flow, another conduit through which air is 'adapted to flow, a main conduit into which ,said branch conduits discharge to provide for mixture of said flows of vapor and air and to provide for conveying the composite iiuid so produced to'a point or points of use or storage, means'for initially proportioning the volumetric rates of ow of vapor and air to provide a compositeVl fluid of a preselected heating Value per unit volume, means for continuouslyascertaining the instantaneous value of the specific gravity ofthe hydrocarbon vapor, means responsive to variations in said instantaneous value with respect to a predetermined value to eect a corresponding variation in the volumetric rate of flow of said hydrocarbon vapor, means for continuously ascertaining lthe instantaneous value of the speciiic gravity of said composite fluid,

means for ascertainingv the diii'erence between the value last mentioned and the proper value of the specific gravity of sai`d composite uid as determined by the ascertained value of the specic gravity of said hydrocarbon vapor, and means for effecting aV further variation in the volumetric rate of flow of. said hydrocarbon fluid in accordance with and to compensate for said difference, whereby a substantially constant heating value per unit volume of said composite uid is maintained.

3. In a gas mixing control system, in combination, a pair of branch conduits through which constituent gaseous fluids are respectively adapted to flow, a main conduit into which said branch conduits discharge to provide a flowing mixture of said fluids, a relatively small pipe through which flows a fluid under pressure, each of said branch conduits having a fixed orifice located therein, devices adapted to respond to the differential value 4of the pressure drops across said orices for effecting movement of said relatively small pipe in one direction or the other,

means including a valve located in one of said branch conduits and movable toward open or closed position through the medium of said iluid under pressureescaping from said relatively small pipe to normally maintain a predetermined ratio between the pressures to be regulated, means including an adjustable device for varying the ra/tio between the pressures aforementioned, and means operable automaticallyl for effecting fadjustment of said device, said last mentioned means including means operable to continuously ascertain and to compensate for variations 'in the instantaneous value of the specific gravity of one of said constituent gaseous fluids, the

y value of the specic gravity'vof the'other of said constituent gaseous iluids beingconstant, whereby the heating value per unit volume of said mixture o f iluids is maintained substantially con-e stant.

4. In a gas mixing control system, in combination, a branch conduit through which a hydrocarbon vaporcf the paraiiine series is adapted to flow, another branch conduit through which air is adapted to ow, a main conduitfinto which said branch'conduits are adapted to jointly discharge to provide a composite ow o1 fluid, means for initially volumetrically proportioning said ilows of vapor and air to provide a composite fluid flow of predetermined heating value per unit volume, meansy i'orcontinuously ascertaining the instantaneous value oi' the specific gravity of said vapor ilow, and means,'espon sive -to` variations inlaid speciilc gravity with respect 'to a preselected value `to automatically eil'ect corresponding variations in the volumetric iates of: owkvof said vapor and said air relavel per unit volume oi' ,said composite fluid ilow is to each other, whereby the heating value air to initially provide a composite iluid of predetermined heating value per unit volume, means including a speciiic gravity meter for continuous` ly ascertaining the instantaneous value of the specic gravity of said vapor, .and associated electrical means controlled by -said meter for automatically varying the relative volumetric rate of ilow of said vapor in accordance with and to compensate for variations in the speciic gravity oi.' the latter, whereby the 'heating value per unit ,10

volume of said composite uid flow is maintained substantially constant.

6. Apparatus for making combustible gas, comprising a container, a quantity of' volatile liquid hydrocarbon of the parailineseries .located within 15 said container, means for controllably venting the vapor generated in said container to provide avapor ilow at a substantially constant predetermined pressure, means for'. effecting a substantially constant volumetrically proportional rate 204 of ilow of air for mixture with said vapor, means for continuously ascertaining the instantaneous value oi' the speciiic gravity of said vapor ow, and means to automatically vary the relative volumetric' rate of ilow of said vapor in response 25 to and to compensate for variations in thevalue of the speciic gravity thereof with respect to a predetermined value, -whereby the heating valuev per unit volume of the owing mixture of vapor and air is maintained substantially constant.

7. In a gas mixing control-system), in combina-- tion means foreiecting a continuous and volu.- metrically constant flow of air at a predetermined pressure, means for effecting a continuous ow of a hydrocarbon vapor of the parafilne series, the volume and pressure of s'aid vapor ilow being definitely proportional to thefvolume and pressure of said ilow of air, means for effecting a ilowing mixture of said ilows of air and vapor' to provide a composite fluid of predetermined' heating value 40 perunit'A volume, meansA for continuously ascertaining the-value of the specic gravity of `said vapor ilow, means Afor varying the volumetric rate of flow of said vapor relatively to the -volumetric rate of ijow of said air in response to and to com- 45 I pensate for variations in the value of the speciiic gravity of said vapor with respect to a preselected value, whereby the heating value per unit volume of said composite fluid is normally: main.

tained substantially constant, means for continu- 50 ouslyascertaining the instantaneous value of the specific gravity of, said composite huid, means `for 'continuously comparing said last mentioned value with the value of the specic gravity of said ow of vapor, and associated means to further vary 55F the volumetric rate of flow of said vapor to maintain a predetermined relationship between 'the values of' said specic gravities, to thereby maintain a prpper relationship betweei4 the volumetric rates of now of the hydrocarbon vapor and 60 air under al1 conditions.

8. Apparatus for proportionihg and mixing gaseous iluids to provide a combustible gaseous mixture ofV substantially constant heating value per unit volume, which,.comprises a branch conduit, means for eiecting a substantially-constant volumetric rate of flow of air through said conduit, a second branch conduit, means for effectlng a ilow of a hydrocarbon vapor oi the paraillne/L series through said second conduit, an adjustable valve in said-second conduit, said valve being initially adjusted to so volumetricallyy proportion the rate .of iiow of said vapor with respect to said rate ofrow of air as to provide a composite ilow of hid oi' .predetermined heating value per unit 75 portionality between the rates of owof air and vapor, means including a specic gravity meter' for continuously ascertaining the value of they. specific gravity of the vapor flowing in said second conduit, means including a -Wheatstone bridge circuit associated with said speciilc gravity meter, means for effecting unbalanclng of said Wheatstone bridge circuit in a sense and to, a degree corresponding with the variation in the value of said specific gravity with respect to a predetermined value, a polarized relayresponsive to the operation of said Wheatstone bridge circuit, and a reversible electric motor controlled by said polarized relay, said motor being. operable automatically to effect adjustment of said differential pressure responsive means to thereby effectI a corresponding adjustment of said valve,'whereby the volumetric proportionality of said flows of vapor and air is varied in accordance with and to compensate for variations in the value of the specific gravity of said vapor, to thereby vmaintain a substantially constant heating value per unit volume of said composite flow of fluid.

9.l Apparatus for proportioning and mixing gaseous fluids to provide a combustible gaseous mixture of substantially constant heating value per unit volume, which comprises a 'branch con-c duit, means for effecting a substantially constant` volumetric rate of flow of air through said conduit, asecond branch conduit, means for effecting a flow of a hydrocarbon vapor of the parafline series through said second conduit, an'adjustable valve -in ysaid second conduit, said valve being initially 'adjusted to so volumetricaily proportion the rate of flow` of said vapor with respect to said rate of flow of air as to provide a-composite vflow of iiuid of predetermined' heating Jvalue'per unit volume 4upon mixture of said vapor and air, a third conduit into which said branch conduits jointly discharge to produce said composite flow of iluid,vmeans including a fixed orifice in each of said branch conduits and differential 'pressure responsive means associated with said orifices for effecting automatic operation of said valve to rnormally maintain a predetermined volumetric proportionalitybetween the rates `of owof air and vapor, means including a lspecific gravity meter for continuously ascertaining the value of vthe specific gravity of the vapor flowing in said having .complementary parts thereof respectively A' associated with 'said specii'lc gravity'meters, a

polarized relay subject to control by said Wheatstone bridge circuit, a reversible electric motor subject to control by said polarized relay, means for effecting adjustment ofsaid differential pressure responsive means according tothe direction and degree of operation of said motor to thereby effect a corresponding adjustment of said valve, means for effecting .unbalancing of said Wheatstone bridge circuit in response to a given operation of saidfirst mentioned specific gravity meter, and means for effecting re-balan'cing of said Wheatstone bridge circuit upon a corresponding loperation of said second mentioned specific gravity meter,.to thereby insure maintenance of a substantially constant heating value per unit volume of said composite ow of uid under all conditions.

10: Apparatus for proportioning and .mixing gaseous `fluids to provide a combustible gaseous mixture of substantially constant heating value per unit volume, which comprises a branch conduit, means for effecting a substantially constant .volumetric rate of flowof air through said conduit, aseco'nd branch conduit, means for effecting a ow of a hydrocarbon vapor of the parailine series through said second conduit, an adjustable valve in said second conduit, said valve being initially adjusted to so volumetricaily vproportion the rate of iiow of said vapor with respect to said rate of flowV of air as to provide a composite iowy of fluid of predetermined heating value per unit volurneupon mixture of said vapor and air, a

third cnduitinto which said branch conduits jointly discharge to produce said composite flow of fluid, means including a fixed orifice in each of said branch conduits and differential pressure responsive means associated with said orifices for` effecting automatic operation of said valve to normally maintain a predetermined-volumetric proportionality between the rates of ow of air and vapor, means including aspecific gravity meter for continuously ascertaining the value of ythe'specic gravity ofthe vapor flowing in said p bridge circuit, a reversible electric motor subject to control by said polarized vrelay, means for effecting adjustment of said differential pressure responsive means accordingto thedirectionand degree of operation of saidmotor to thereby effect a corresponding adjustment of said valve,

means for effecting unbalancing'of said Wheatstone bridge circuit in response to a given 'opera-' tion of said first mentioned specic'gravity meter,

and means for effecting rebalancing; of said operation of said second mentioned specific gravity meter, to thereby insure maintenance of a substantially constanty heating value per unit volume of said composite flow of uid under all'conditions, the aforementioned means ,including means operable automatically for effecting adjustment of said valve in steps in response to unbalancing of said Wheatstone bridge circuit. byy

said specific gravity meter first mentioned, to thereby provide for ascertainment of the s cific gravity of. said composite flow of fluid by said second mentioned specific gravity meter prior Ato a further adjustment of said valve.-

11. The method of making combustible gas, which cemprises effecting a continuous flow of air at a pre etermined pressure; effecting a continuous flow of a hydrocarbon vapor of .the paraflne Wheatstone bridge circuit` upon a corresponding series the. specific gravity of whichis subject to inherent variations, the volume and pressure ci' said vapor flow' being definitely proportioned with vapor ow, and utilizing variations in the instantaneous value of the specific gravity of said vapor with respect to a preselected value to effect corresponding variations in the relative volumetric rates of flow of said, vapor and said ain-whereby the heating=value perunit volume of said composite iluid is maintained substantially constant.f

12. rl`l1e method of making combustible gas, which comprises depositing within a closed container a volatile liquid hydrocarbon of the parafr i'lne series, controllably venting the vapor gener- .ated in said container to initially provide a predetermined volumetric rate of Vapor flow at a substantially constant predetermined pressure, the specific gravity of said vapor being subject to inherent variations, effecting a substantialhr constant volumetrically proportional rate of flow of air for mixture with said vapor, continuously ascertaining the instantaneous value of the specic gravity of said vapor ow, and utilizing vari-` ations in the instantaneous value'of the specific gravity of said vapor flow with respect 4to a predetermined valueto effect corresponding'variations in the relative volumetric rate of flow of said vapor, whereby the heating value per unit volume cf the flowing mixture of vapor and air is maintained substantially constant. e

13. The method which comprises effecting `a continuous and volumetrically constant flow of air at a predetermined pressure, effecting a continuous flow of a hydrocarbon vapor of the paraffine series the specific gravity of whichis subject to inherent variations, the volume and pressure of said vapor flow being initially ldefinitely proportional to the volume and pressure, respectively, of said flow of air, effecting a owing mixture of said flows of air and vapor to provide a composite fluid of predetermined heating value per unit volume, continuously ascertaining the instantaneous value of the specific gravity of said vapor flow, and utilizing variations in the instany taneous value of the specific gravity of said vapor with respect to a preselected value to effect corresponding variations inthe volumetric rate of 45 flow of said vapor relatively to the volumetric rate of flow of said air, whereby the heating value per unit volume of said composite fluid is maintained substantially constant. y e

I14. The method `which comprises effecting a continuous and volumetricallyconstant flow of air at a predetermined pressure, effecting a continuous flow of a hydrocarbon vapor. of the paraiiineseries the specific gravity of which is subject to inherent variations, the volume and pressure of said vapor ow being definitely proportional to the volume and pressure, respectively, of said flow of air, initially effecting a flowing mixture of said ows of air and vapor to provide a composite fluid of predetermined heating value per unit volume, continuously ascertaining the instantaneous value of the specific gravity of said vapor ow, utilizing variations in the instantaneous value of the specific gravity of said vapor with respect to a preselected value to effect corresponding variations in the volumetric rate of 'ow of said vapor relatively to the volumetric rate of flow of said air, whereby the heating value per unit volume of said composite fluid vis normally maintained substantially constant, continuously ascertaining the. instantaneous value of the specific gravity of said composite uid, continuously comparing said last mentioned value with the value of the specific gravity of said flow of vapor, and utilizing the difference in said values to effect a further variation in the volumetric rate of flow of said vapor tomaintain a predetermined 'relationship between the values of said specific gravities, to thereby maintain a proper relationship between the volumetric rates of flow of the hydrocarbonvvapor and air under all conditions.

15. The method of mixing combustible gases to provide a combustible mixture having a predetermined substantially constant heating value per unit volu/me regardless of inherent variations in the specific gravity of said mixture, which compri'ses effecting a predetermined substantially constant volumetric rate of flowof air, effecting an initially volumetrically proportioned-flow of a hydrocarbon vapor of the paraine series the specic gravity of which is subject to inherent variations, effecting a mixture of said vapor and air to provide a composite fluid of predetermined heating value per unit volume, continuously ascertaining the instantaneous value of the specic variations. in the value of said specific gravity with vrespect to a predetermined value' to substantially simultaneously eiect corresponding variations in the volumetric rate of flow of said lvapor, whereby the heating value per unit volume maintained substangravity of said hydrocarbon vapor, and utilizing the specific gravity of said mixture, which comprises effecting a predetermined substantially constant volumetric rate of flow of air, effecting an initially volumetrically proportioned flow of a hydrocarbon vapor of the paraffine series the specific gravity of which is subject to inherent variations, effecting a mixture of said vapor and air to provide a composite uid of predetermined heating value per unit volume, continuously ascertaining the instantaneous v'alue of the specific gravity of said hydrocarbon vapor, utilizing variations in. the instantaneous value of said specific gravity with respect to a predetermined value to substantially simultaneously effect corresponding variations in the volumetric rate of flow o'f said vapor, whereby the heating value per unit volume of said composite fluid is maintained substantially constant, predetermining the proper value of the specific gravity of said composite fluid to be malntained in respect of each given-'value of the specic gravity of said hydrocarbon vapor, continuously ascertaining the instantaneous value of the specic gravity of said composite fluid, and

utilizing variations in said last mentionedvalue with respect to said predetermined proper value 

